1. Field of the Invention
The present invention relates to a die cushion device for a press machine capable of regenerating energy to achieve high energy efficiency.
2. Description of the Related Art
A die cushion device is defined as a device that clamps a workpiece between the blank holder and the upper die of a press machine and applies a blank holding force (a cushion force) to the workpiece.
For some time, there have been proposed various types of die cushion devices as the die cushion device for a press machine (for example, refer to Patent Documents 1 to 3).
Patent Document 1 discloses a hydraulic force increasing linear motor type, and Patent Documents 2 and 3 disclose a ball screw type.
As shown in FIG. 1, the die cushion device of Patent Document 1 includes a body container 51; a movable body 52 which is movable along the inner wall of the body container 51; a cylinder 53 which is connected to communicate with the inside of the body container 51; a stator 57 which is installed at the cylinder 53; a piston head 54 which slides along the inner wall of the cylinder 53; a piston rod 55 which is attached to the piston head 54; and a mover 58 which is connected to the piston rod 55, wherein a hydraulic fluid L is commonly accommodated in the body container 51 and the cylinder 53 and is also sealed by the movable body 52 and the piston head 54, wherein the cross-sectional area of the cylinder 53 is smaller than that of the movable body, wherein the stator 57 and the mover 58 constitute a linear motor, wherein the linear motor is driven to make the piston head 54 slide on the inside of the cylinder 53 via the piston rod 55 so that the hydraulic fluid L accommodated in the cylinder 53 flows into or from the body container 51 to move the movable body 52.
The die cushion device disclosed in Patent Document 2 is adapted to drive a ball screw using a force applied from a servo motor via a deceleration mechanism such as a timing belt.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2008-280907, “LINEAR MOTOR TYPE PRESSURIZATION PUMP AND DIE CUSHION DEVICE HAVING THE SAME”
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2006-000908, “DIE CUSHION DEVICE”
[Patent Document 3]
Japanese Patent Application Laid-Open No. 2006-055872, “DIE CUSHION DEVICE”